1. Field of the Invention
The present invention relates generally to optics and more particularly, to coherent optical amplifiers of a light field scattered by an object that is not just a signal beam, and can be used to perform surveillance, and active or passive tracking of the object.
2. Description of the Related Art
Active laser surveillance (ALS) can be used for tracking and comprehensive characterization of distant objects. For example, ALS can be used for active and passive space surveillance for pinpointing relatively small but still potentially devastating meteorites, comets, and debris that threaten to strike terrestrial or manmade space objects, such as a spacecraft. Early detection of these objects would provide an advanced alert to allow time for safety actions, such as evacuation of threatened areas on the ground or change of orbital parameters in the case of spacecraft. However, considering the distances involved, active detection and imaging of such remote objects remains a task that is very difficult to fully achieve due to the low level of intensity of backscattered light signals. Attempts to amplify the backscattered light by using currently available methods result in amplification of the noise associated with the signal, and so is of limited use.
Similar issues arise regarding imaging and surveillance of ground facilities or objects of interest, such as state borders, military bases, ports, bridges, reservoirs, and in the private sector, such as sports arenas, airports, malls, industrial buildings, and other large public buildings. For example, when used for a covert surveillance mission, low-level illumination intensity is preferred to reduce the probability of its detection from the object under surveillance. However, this low-level illumination intensity results in a low-intensity backscattered light field which makes it harder to detect by the surveillance module. Other scenarios that require low-intensity coherent imaging include behavioral studies of live species and microorganisms that often do not tolerate a high-intensity illumination.
Accordingly, there is a need for a system and method of amplifying a laser signal that overcomes the shortcomings stated above.